Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$53.28	6.176%	$56.5706	$56.57	$56.55	$56.60
Purchase #2	$165.68	9.605%	$181.5936	$181.59	$181.60	$181.60
Purchase #3	$158.74	13.364%	$179.954	$179.95	$179.95	$180.00
Purchase #4	$117.87	10.809%	$130.6106	$130.61	$130.60	$130.60
Purchase #5	$177.66	6.140%	$188.5683	$188.57	$188.55	$188.60
Purchase #6	$132.78	4.211%	$138.3714	$138.37	$138.35	$138.40
Purchase #7	$167.44	11.874%	$187.3218	$187.32	$187.30	$187.30
7 purchase totals =	$973.45		$1,062.9903	$1,062.98	$1,062.90	$1,063.10